Honeycomb filter structures for DPF (Diesel Particulate Filters) are widely known in the prior art. Such honeycomb filter structures have a structure wherein some of the through-holes of a honeycomb structure having a plurality of through-holes have one of their sides plugged with a plugging material, while the other sides of the remaining through-holes are likewise plugged with a plugging material. In Patent documents 1 and 2 there are disclosed a die and extrusion-molding device to be used for production of a honeycomb structure.